The goal of this research program is to develop an expeditious and stereospecific total synthesis of the cytotoxic antibiotic pentalenolactone. Pentalenolactone is an acidic lipophylic antibiotic isolated from the fermentation broth of Streptomyces UC 5319 which exhibits inhibitory activity against nucleic acid synthesis in bacterial cells. The antibiotic has an unusual pentalene skeleton which is annulated with a six membered lactone ring bearing an alpha-epoxide moiety. To date we have succeeded in preparing 3,4-dimethyl-cis-(3.3.0)-3-octene-2,8-dione; a potentially useful synthon for the construction of the natural product pentalenolactone. The synthesis of the dione starts from 2-methyl cyclopentane-1,3-dione and utilizes a conjugate addition reaction of the kinetic enolate derived from the vinylogous ester analogue of the latter dione. Alkylation and reductions of the pentalenedione system salient to the preparation of the target molecule have been developed.